Monitoring risk-adjusted medical outcomes allowing for changes over time

• Published in: Biostatistics (Oxford, England) Vol. 15; no. 4; pp. 665 - 676
• Main Authors: Steiner, S. H., Mackay, R. J.
• Format: Journal Article
• Language: English
• Published: England Oxford Publishing Limited (England) 01.10.2014
• Subjects: Biostatistics; Cardiac Surgical Procedures - mortality; Cardiac Surgical Procedures - standards; Cardiac Surgical Procedures - statistics & numerical data; Failure analysis; Humans; Likelihood Functions; Outcome and Process Assessment (Health Care) - standards; Outcome and Process Assessment (Health Care) - statistics & numerical data; Risk Adjustment; Risk assessment; Surgical outcomes; Exponentially weighted moving average; Likelihood; Weighted estimating equation; Score function
• ISSN: 1465-4644; 1468-4357; 1468-4357
• DOI: 10.1093/biostatistics/kxt057

We consider the problem of monitoring and comparing medical outcomes, such as surgical performance, over time. Performance is subject to change due to a variety of reasons including patient heterogeneity, learning, deteriorating skills due to aging, etc. For instance, we expect inexperienced surgeons to improve their skills with practice. We propose a graphical method to monitor surgical performance that incorporates risk adjustment to account for patient heterogeneity. The procedure gives more weight to recent outcomes and down-weights the influence of outcomes further in the past. The chart is clinically interpretable as it plots an estimate of the failure rate for a "standard" patient. The chart also includes a measure of uncertainty in this estimate. We can implement the method using historical data or start from scratch. As the monitoring proceeds, we can base the estimated failure rate on a known risk model or use the observed outcomes to update the risk model as time passes. We illustrate the proposed method with an example from cardiac surgery.